Different types of electrocardiographs and cardiac monitors are known in the art and, in this sense, a great deal of work has been developed to simplify these pieces of equipment without losing the accuracy and reliability of the signals obtained and processed.
It is known that electrocardiographs are devices that detect electrical signals associated with the activity of the heart in order to produce electrocardiograms (ECG), which basically consist of a graphical record of the electrical voltage as a function of time. Therefore, an ECG consists of a non-invasive medical diagnostic method widely used in the follow-up of cardiac pathologies and routine examinations.
The first enhancements to the electrocardiographs date from 1872, and currently a great deal of effort is put into the development of increasingly simpler, portable and personal pieces of equipment enabling their use by the users/patients themselves outside the hospital environment.
Typically, the record of the heart's electrical activity is made through electrodes or sensors placed on specific points of the user's body surface. These electrodes sense the sequences of electrical events occurring in the cardiac cycle (systoles and diastoles) and which propagate to the body surface, these events later being processed and extracted into ECG graphs.
For sensing these electrical cardiac signals, predetermined points are respected on which said electrodes should be positioned. This distribution of electrodes at predetermined points is known as lead, and usual leads are bipolar leads, unipolar leads and unipolar precordial leads. For each type of lead, a certain number of electrodes is used and arranged on different positions. Thus, traditional electrocardiographs formed by wires with sensors or electrodes at one of their ends are widely used, these electrodes being positioned on the user in the following manner: two electrodes on the arm, one electrode on the left leg and six electrodes distributed on the thoracic region. A simpler variation of this traditional method uses three wires with electrodes on one of the ends and two or four more electrodes (depending on the model) housed on the surface of the apparatus.
Because of the excessive quantity of wires used in traditional electrocardiographs, two color codes have been assigned in an attempt to standardize and simplify the handling of these wires. In the first code, the following colors are used: red, green and yellow, and handling should be done as follows: green on the waist region of the patient's left side; red on the right hand, wrist and axilla; yellow on the left hand, wrist and axilla. In the second code, the following colors are used: white, black and red, and handling should be done as follows: red on the waist region of the patient's left side; white on the right hand, wrist or axilla and black on the left hand, wrist or axilla. With regard to the sensors on the surface of the apparatus, they are positioned on the patient's thorax in three positions that vary from the center of the thorax to the left lateral region, next to the ribs.
An inconvenience presented by these traditional electrocardiographs consists of the large amount of color-coded wires used, requiring a trained professional skilled in performing the examination, thus avoiding the use of these pieces of equipment by lay users. This becomes a problem in the case of an emergency wherein the patient to be treated is not in a hospital environment, for instance, in case the patient has cardiac complications at home, these devices cannot be used by those accompanying the patient to identify the reasons for his/her indisposition. This leads to the need for urgent removal of the patient to a hospital and a relative delay until the heart problem is actually detected and confirmed.
Another disadvantage is in the lower durability of the wires in relation to the other components of the equipment, requiring extra handling. Furthermore, the inadequate handling of the wires increases the incidences of noise and interference in the sensing of the signal, which may affect the quality of the data sensed as well as the ECG graph obtained.
In order to solve this problem, document US 2002/0045836 discloses multiple wireless sensor assemblies for individually attachment to standard body locations for ECG signal recording. This system does not use wires once the electrodes are comprised within an housing with an integrated circuit and a wireless transmitting device. Nevertheless, this system needs at least two housings with electrodes in order to obtain a complete ECG bipolar, unipolar or unipolar precordial measurement. Additionally, several placements of the housings are required. This results in difficult handling and a non intuitive method, requiring a trained professional skilled in performing cardiac examination.
The document WO 02/089667 also discloses an apparatus for monitoring an electrical signal from a patient's body including a disposable patch with a plurality of electrodes, a converter, a processor and a transmitter for transmitting the processed digital signal as wireless signal. This system can monitor different electrical impulses by various organs by placing the disposable electrode patches on the selected organ. One of the possible measurements is an electrocardiogram. However, this document only describes that it can do electrocardiogram measurements, but it does it does not describe that the electrode patch can perform a complete (twelve leads) electrocardiogram measurement by different positioning of one electrode patch.